<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>for...in的遍历性</title>
</head>
<body>
<script>
    function F(){
        this.a="a";
        this.b="b";
    }
    F.prototype.c="c";
    var m=new F();
    for(var a in m){
        console.log(a);//a b c  所以他会遍历原型上的属性
    }
</script>
</body>
</html>